Its just another way to to eat up your money....
Guys.. there is no point in doing it. The service centre guy out, uses some cheap oil after they drain out all your existing oil and then keep the vehicle in start mode for few minutes. and after draining out this they pour the new oil. That's all what they do.
Its just like we gargle our mouth, before we drink some water...

And to add more its noticed that some of them keep using the same oil for flushing purpose for a quite some time for all the cars.......